O'ahu residents and businesses will pay about 50 percent more for water by 2010 under a five-year rate-increase plan approved yesterday by the Honolulu Board of Water Supply.

A typical O'ahu household will see its bimonthly water bill rise in five annual steps, beginning Oct. 1, from $49.72 now to $76.24 on July 1, 2010.

The board last raised rates in 1995. But the agency needs more money to cope with rising construction, fuel and electricity costs, it said.

"The (Board of Water Supply) has worked hard over the years to control costs and has been able to defer scheduled rate increases since 1995," Clifford P. Lum, board manager and chief engineer, said in a written statement.

"However, we can no longer afford to postpone rate increases. We need the additional revenue to keep up with uncontrollable cost escalations, and most importantly, to properly and proactively address the needs of our aging infrastructure."

The agency anticipates spending $2.8 million in fiscal year 2005-06 for emergency road repaving, which it takes care of after fixing broken water mains. That's a nearly a ninefold increase from 1995, the board said.

The price of plastic pipe has jumped 29 percent in the past year, while ductile iron pipe is up 18 percent and steel pipe 9 percent.

The board spent $13.6 million in 2005 on electricity to run its pumps, a 34 percent increase from 1995. Its fuel costs went up 94 percent in that period to $461,000 in 2005.

Salaries and other personnel costs increased 18 percent in the past two years, to $31 million for 583 employees this year.

The board now charges $1.77 per thousand gallons of water for the first 13,000 gallons used each month.

The rate goes up to $2 per thousand gallons on Oct. 1; $2.24 on July 1, 2007; $2.46 on July 1, 2008; $2.66 on July 1, 2009; and $2.79 on July 1, 2010.

Each household's bimonthly bill also includes a $3.70 billing charge.